The present invention relates to an image data output apparatus for accessing image data representing an image area crossing adjacent pages, and displaying and/or printing it, to output an image. The image data output apparatus can be used effectively in an electronic file system or the like.
In a conventional electronic file system capable of displaying and/or printing image data such as a map and a picture, many pieces of image data are stored in a disk system such as an optical disk system, each image data representing a page corresponding to one frame. The stored data is read out and edited as required.
In such a conventional system using an optical disk apparatus, image data is input/output in units of pages (a one-frame image is recorded in one track, and an address is assigned to each track and is accessed to input or output data), as is shown in Japanese Patent Disclosure (Kokai) No. 58-150137 (disclosed on Sep. 6, 1983).
To output a large image crossing adjacent pages, such as a map, all portions of the large image must be displayed or printed. This is impossible. Therefore, pages associated with the large image are printed as hard copies, and these copies are cut to extract associated portions. These portions are then adhered to each other to form the large image. The user must always pay attention to the units of pages, when operating the conventional image data output apparatus. Hard copies include wasteful portions. Necessary portions of the hard copies must be adhered together by means of glue or the like.
Japanese Patent Disclosure (Kokai) No. 55-57936 (disclosed on Apr. 30, 1980) discloses an image data output apparatus having a CRT memory for storing image data of one or more frames, to display a large image (e.g., a map) which cannot be displayed as a one-frame image on the CRT screen. The display screen is scrolled in any direction, to observe a desired portion. However, a screen to be scrolled, in order to cover a wide area on the CRT display device, is not preferable since the memory capacity must then be increased.
In order to avoid increasing the memory capacity in the CRT display device, it is detected in advance that a display area has reached the end of the CRT screen, while the display area is being shifted, and then the memory blocks are reallocated. The image data is supplied from a computer to the reallocated CRT memory, so that an image in the moving direction can be observed.
However, if a storage medium, such as an optical disk for storing image data in units of pages (in units of frames) is used, and such data is read out or written therein, it is difficult to achieve accurate, arbitrary, high-speed accessing of image data representing an area crossing adjacent pages.